Q: Would it harm a tree if I built a simple treehouse in it? It would be nothing elaborate: a deck, three walls, and a roof. I was thinking of the nails that would have to be used to make firm steps for my grandchildren and for the support braces. A: A few nails or bolts in a tree trunk will not harm the tree. The tree needs to be solid to begin with, or else the holes could allow insects and water to enter the trunk. The ladder going up to the tree can be attached to the house instead of the tree trunk to reduce the number of nails into the trunk. A treehouse can be built so it is around a tree trunk without actually being attached to the tree. The weight of the house doesn’t have to be entirely supported by the tree. Support posts can …